September 1, 2009 Feature

Are Your Hearing Aid Fittings "On Target"?

Hearing aid verification and validation may be underutilized, according to recent surveys of dispensing audiologists (Strom, 2006) and ASHA-certified audiologists (ASHA, 2008). Hearing aid verification is the process of confirming prescribed electroacoustic performance of hearing aids, usually gain and maximum output, in the wearer's ear; validation is the process of confirming the benefits provided by amplification to the wearer.

In the survey by Strom (2006), 68% of dispensing audiologists reported owning real-ear measurement (REM) equipment, the tool of choice for verification (e.g., Humes, Block, & Hipskind, 1988), but only 16% reported using it on a routine basis. Although the sample included in Strom (2006) involved only 54 dispensing audiologists, the 2008 ASHA Audiology Survey included responses from 2,181 ASHA-certified audiologists, about 364 of whom owned their own practice and 80.3% of whom indicated that they fitted and dispensed hearing aids. About 55% of the ASHA-certified audiologists indicated that they provided REM as a service, but with no indication of how frequently or routinely this service is provided.

Strom (2006) reported that when validating the outcome of a hearing aid fitting, 49% of dispensing audiologists used some form of speech-in-noise testing and 77% used self-report surveys. Unfortunately, of those who use self-report surveys, about 60% used their own survey rather than a carefully researched standardized instrument. About 38% of ASHA-certified audiologists indicated that they validated "treatment outcomes by self-questionnaire," but additional details regarding the nature of that self-questionnaire are not available (ASHA, 2008).

Together, these survey results are disappointing regarding real-ear verification and validation of outcome by practicing audiologists. Ample evidence demonstrates the effectiveness of real-ear verification and its importance as a clinical tool (e.g., Mueller, 2005; Mueller & Bentler, 2005). Perhaps practicing audiologists rely on the hearing-aid manufacturer's software for verification and assume that the accuracy of the computer's software and the precision of digital hearing aids are sufficient to generate close matches to targets or to simulate such matches effectively. Research on both gain (Hawkins & Cook, 2003) and maximum output (Mueller, Bentler, & Wu, 2008), however, provide strong evidence that such an assumption is flawed.

Use of average data, or computer simulations of matches to target gain and output, is not an acceptable alternative to actual verification in the wearer's ear canal. Of course, this is even more relevant with fittings for pediatric or special populations for whom individually measured real-ear-to-coupler differences (RECDs) have proven helpful (Strauss & van Dijk, 2008). Although time is required to perform REM, it is one of the more efficient clinical measurements available to audiologists. The negative consequences to the hearing aid wearer can be great when the audiologist simply fails to take a relatively brief amount of time to verify gain and output in the wearer's ear.

Validating Benefit

Perhaps even more important than verification is validation of the benefits of amplification to the wearer. The patient typically arrives at the clinic complaining it is difficult to hear and understand speech, and difficult to communicate or hear important sounds in everyday life. It is important for the practitioner to demonstrate to the patient (or third-party payer) that amplification provides tangible benefits.

In a series of research studies conducted over the past decade at Indiana University (e.g., Humes, 2003, 2007), we have demonstrated that at least three aspects or dimensions of hearing-aid outcome should be measured:

  • Aided and unaided speech understanding, preferably in noise under listening conditions representative of everyday communication
  • Self-reported hearing-aid usage (or data-logging)
  • Self-reported "benefaction," a combination of measures of benefit and satisfaction

Humes et al. (2009) recently described a brief but comprehensive approach to the measurement of hearing aid outcome along each of these dimensions and provided norms to interpret the results of these measurements obtained from individual patients. After two decades of extensive surveys of tens of thousands of hearing aid purchasers, Sergei Kochkin noted that the two best ways to improve wearer satisfaction are through counseling time and the measurement of outcome (Strom, 2005). We agree and believe that with verification and validation, an increasing number of hearing-aid fittings will be truly "on target."

Larry E Humes, PhD, CCC-A, is professor in the Department of Speech and Hearing Sciences at Indiana University in Bloomington. Contact him at humes@indiana.edu.

Nathan E Amos, PhD, CCC-A, is clinical associate professor in the Department of Speech and Hearing Sciences at Indiana University in Bloomington. Contact him at namos@indiana.edu.

cite as: Humes, L. E.  & Amos, N. E. (2009, September 01). Are Your Hearing Aid Fittings "On Target"?. The ASHA Leader.

Resources

Look for more information on verification and validation in the upcoming January/February 2010 issue of the Access Audiology e-newsletter. To subscribe or to read past issues, visit the ASHA Web site.



References

American Speech-Language-Hearing Association (2008). 2008 Audiology Survey summary report: Number and type of responses. Rockville, MD: Author.

Hawkins, D.B., & Cook, J.A. (2003). Hearing aid software predictive gain values: how accurate are they? The Hearing Journal, 56(7), 26, 28, 32.

Humes, L.E., Hipskind, N. & Block, M. (1988). Insertion gain measured with three probe tube systems. Ear and Hearing, 9, 108–112.

Humes, L.E. (2003). Modeling and predicting hearing-aid outcome. Trends in Amplification 7(2), 41–75.

Humes, L.E. (2007). Hearing-aid outcome measures in older adults. In Palmer, C.A. and Seewald, R.C. (Editors), Hearing Care for Adults 2006, Phonak AG: Stafa, Switzerland, pp. 265–276.

Humes, L.E., Ahlstrom, J.B., Bratt, G.W., & Peek, B.F. (2009). Studies of hearing aid outcome measures in older adults: A comparison of technologies and an examination of individual differences. Seminars in Hearing, 30, 112–128.

Mueller, H.G. (2005). Fitting hearing aids to adults using prescriptive methods: An evidence-based review of effectiveness. Journal of the American Academy of Audiology, 16, 448–460.

Mueller, H.G., & Bentler, R.A. (2005). Fitting hearing aids using clinical measures of loudness discomfort: An evidence based review of effectiveness. Journal of the American Academy of Audiology, 16, 461–472.

Mueller, H.G., Bentler, R.A. & Wu, Y.-H. (2008). Prescribing maximum hearing aid output: Differences among manufacturers found. The Hearing Journal, 16(3), 30–36.

Strauss, S., & van Dijk, C. (2008). Hearing instrument fittings of pre-school children: Do we meet the prescription goals? International Journal of Audiology, 47(Suppl. 1), S62–S71.

Strom, K.E. (2005). HR interviews Sergei Kochkin, PhD. The Hearing Review, 12(11), 24–32, 82.

Strom, K.E. (2006). The HR 2006 dispenser survey. The Hearing Review, 13(6), 16–39.



  

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